The tub not only holds the weight of the water and the articles to be washed, but also supports the static and dynamic charges which are generated with the washing or centrifuge motions, some of which can be large enough to deform the shape of the tub, knowing that these are generally manufactured by thermoplastic injections, the most popular being polypropylene. So, for example, when the basket is turning at a high speed in order to achieve centrifuge it is very common that the weight of articles to be washed in the basket cause an imbalance of the system, which cause the basket to not only have a rotational movement but also a translational one within the tub, even causing possible scraping against the tub's internal wall, not a desired effect of the design. If this occurs in addition to the deformation caused in the tub's mouth, the gap between the basket and the tub is greatly reduced.
This is why it is necessary to design a tub for a top loading washer which is highly rigid, not discounting the difficulty of manufacture, using thermoplastics like polyethylene or polypropylene, which help absorb, distribute and transmit the different forces and efforts created by the varying washing and centrifuge cycles.
Various efforts in this area have taken place with said objectives in mind, such as Paul Gregory Hall's AU2006235808 patent application which deals with a pumping system which is fastened to the lower portion of the tub; FIG. 2 shows a cross section of the lower portion of the tub where the reinforcements of the inferior external part of the tub can be seen, where a pancake type motor is grasped emphasizing the pump's assembly, the part of particular interest in this tub being the use of lobes in the tub's superior part which are aligned with the reinforcement of the support ears.
Jonathan David Hartwood's et al EP 1 783 264 A2 published patent application which presumably shows in FIG. 2, the same tub as Hall's, where there appear a pair of lobes aligned with the ear reinforcements, wherein said lobes were presumably designed to create more space for the basket inside the tub, given their number, as it only is comprised of two lobes which do not significantly increase the area's rigidity in the tub's mouth, allowing a larger space to the basket as well as to the tub's cover which can house a grid, window or passage in the precise additional area created by the lobes intended to transport chemicals deeper into the tub to be mixed with greater ease.
Even so, though the tubs shown in both documents at a simple glance appear to have strong reinforcements at the ears making them better able to hold heavy loads, no concern seems to be given to avoiding the deformation neither to the tub's mouth nor to the tub's cylindrical wall with an end result of attaining a more rigid tub which supports, absorbs, cushions and transmits the forces generated inside the basket while washing or centrifuge motions take place.
Given the above discussion, the need to develop a tub with higher rigidity yet using the traditional manufacturing materials, thereby reducing cost becomes apparent. The tub also allows for larger baskets to be held due to lesser deformities and thus transmits more efficiently the efforts to the suspension rods with shock absorbers, and also avoids the scraping between the tub and the basket during centrifuge, where larger baskets allow for larger washing loads as well as water and detergent (mixes water with chemicals or additives), allowing for larger washing loads in an equal volume sized cabinet, this being the purpose of this invention.